Effects of a Fish Oil Rich in Docosahexaenoic Acid on Cardiometabolic Risk Factors and Oxidative Stress in Healthy Rats

Omega-3 polyunsaturated fatty acids are associated with a lower risk of cardiometabolic diseases. However, docosahexaenoic acid (DHA) is easily oxidized, leading to cellular damage. The present study examined the effects of an increased concentration of DHA in fish oil (80% of total fatty acids) on cardiometabolic risk factors and oxidative stress compared to coconut oil, soybean oil, and fish oil containing eicosapentaenoic acid (EPA) and DHA in a balanced ratio. Forty healthy male Sprague–Dawley rats were supplemented with corresponding oil for 10 weeks. Supplementation with the fish oil containing 80% DHA decreased plasma fat, plasma total cholesterol and muscle fat compared to the coconut oil and the soybean oil. Increasing concentrations of DHA induced incorporation of DHA and EPA in cell membranes and tissues along with a decrease in ω-6 arachidonic acid. The increase in DHA promoted lipid peroxidation, protein carbonylation and antioxidant response. Taken together, the increased concentration of DHA in fish oil reduced fat accumulation compared to the coconut oil and the soybean oil. This benefit was accompanied by high lipid peroxidation and subsequent protein carbonylation in plasma and in liver. In our healthy framework, the slightly higher carbonylation found after receiving fish oil containing 80% DHA might be a protecting mechanism, which fit with the general improvement of antioxidant defense observed in those rats.     

Dietary methionine affects growth and the expression of key genes involved in hepatic lipogenesis and glucose metabolism in cobia (Rachycentron canadum)

Juvenile cobia (Rachycentron canadum), a carnivorous fish, was chosen to examine the effects of methionine (Met) supplementation of low fishmeal diets on growth and the expression of key genes related to hepatic lipogenesis and glucose metabolism. Seven isonitrogenous and isolipidic diets were formulated to contain 7.2, 9.0, 10.0, 12.4, 14.1, 16.3 and 18.6 g/kg dietary Met levels. Healthy cobia (initial average weight ± SE = 9.79 ± 0.04 g) were randomly assigned into seven groups in triplicate with 40 individuals per sea cage for 8 weeks. The results showed that the weight gain rate (WGR) of fish increased as the dietary Met was increased up to 12.4 g/kg and then decreased. The expression of insulin‐like growth factor‐I (IGF‐I) and target of rapamycin (TOR) genes was inhibited by the Met‐deficient diets. The mRNA levels of fatty acid synthase (FAS) and sterol regulatory element‐binding protein‐1 (SREBP1) genes increased with increasing dietary Met until 12.4 g/kg after which the former remained constant, whereas the latter decreased from 12.4 to 18.6 g/kg Met. The mRNA levels of pyruvate kinase (PK) increased as the dietary Met levels increased, reaching a peak at 12.4 g/kg, and then decreased with further increases in Met. However, the mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) decreased as the dietary Met was increased up to 12.4 g/kg and then remained constant from 12.4 to 18.6 g/kg Met. In conclusion, based on the straight broken‐line analysis of WGR against dietary Met levels, the optimal dietary Met requirement for juvenile cobia was estimated to be 12.4 g/kg (26.9 g/kg dietary protein). A diet with the optimal level of Met induces fish growth and is associated with increased IGF‐I and TOR.     

Effect of recombinant crustacean hyperglycemic hormones rCHH‐B1 and rCHH‐B2 on lipid metabolism in the Pacific white shrimp Litopenaeus vannamei

The crustacean hyperglycemic hormones (CHH) are pleiotropic neuropeptides controlling diverse processes in the life cycle of crustaceans. In the Pacific white shrimp Litopenaeus vannamei, CHH‐B1 and CHH‐B2 are generated by alternative splicing of the same gene, and the recombinant versions of these peptides have shown differential effects on glucose metabolism and osmoregulation in this species. In this work, we explored the role of both recombinant variants, expressed in yeast Pichia pastoris, on lipid metabolism. The results showed that rCHH‐B1 and rCHH‐B2 injections into eyestalk‐ablated shrimp significantly increased the phospholipid and triglyceride levels in haemolymph and restored free fatty acid levels, suggesting that these CHH variants mobilize lipid reserves in shrimp. The effects on lipids were concomitant to its hyperglycemic activity, suggesting that both variants, in addition to their hyperglycemic activity, have hyperlipidemic functions.     

Rumen-protected glucose supplementation in transition dairy cows shifts fermentation patterns and enhances mucosal immunity

Manipulation of perinatal diets, such as supplementing feed with rumen-protected glucose (RPG), has been positively regarded as a strategy to improve milking performance. This study was conducted to assess the effects of RPG on the fermentation profiles, resident microbiota and mucosal immunity in the cecum. Ten Holstein dairy cows were randomly assigned to either a 25 g/kg RPG diet (DM basis) or a 11 g/kg coating fat diet (control, CON). Compared with the CON group, the acetate-to-propionate ratio was lower in the RPG group. Gene expression analysis indicated that RPG supplementation tended to upregulate the expression of Na⁺/H⁺ hydrogen exchanger 3 (NHE3) (P = 0.076). RPG supplementation downregulated the expression of genes involved in self-rehabilitation such as matrix metalloproteinase 1 (MMP1), MMP3, MMP9 and MMP13. Additionally, the mRNA expression of genes involved in immunity including Toll-like receptors (TLR4, TLR6 and TLR7) and proinflammatory cytokines (immune interferon gamma [IFNG] and interleukins interleukin 17A [IL17F], IL17A, IL22), was downregulated by RPG supplementation. Nonetheless, no differences existed in the bacterial copy number and beta diversity between the 2 groups. Overall, supplementation with RPG would probably cause a shift towards propionate production in the cecal digesta, and promote the immune homeostasis of the cecal mucosa in transition dairy cows. Our results extended the basic understanding of RPG supplementation and utilization in transition dairy cows in terms of host microbe interplay in the cecum.     

Study on the Mechanism of the Blood-Glucose-Lowering Effect of Collagen Peptides from Sturgeon By-Products

In a previous study, we found that the collagen peptides prepared from the by-products of Bester sturgeon had an inhibitory effect on elevated blood glucose levels in a glucose tolerance test with ICR mice. In the present study, we examine the mechanism of the effect of sturgeon collagen peptides (SCPs) in detail. When glucose was orally administered to mice along with the SCPs, it was found that the glucose remained in the stomach for a longer time. In the above tests, the amount of glucose excreted in the feces of mice also increased. On the contrary, it was revealed that the SCPs have a dipeptidyl-peptidase-IV (DPP-IV) inhibitory ability in an in vitro test. In subsequent oral and intravenous glucose administration tests, glucagon-like peptide-1 (GLP-1) and insulin levels in the blood of mice were maintained at high levels. These results suggested the following three mechanisms: SCPs slow the rate of transportation of glucose from the stomach into the small intestine, resulting in delayed glucose absorption; SCPs suppress the absorption of glucose in the small intestine and excrete it from the body; SCPs inhibit DPP-IV in the blood and maintain a high GLP-1 level in blood, which in turn stimulates insulin secretion.     

饲料糖脂比对吉富罗非鱼生长、生理生化指标、肠道菌群组成及抗病力的影响

为研究不同糖脂比饲料对罗非鱼幼鱼生长、生理生化指标、肠道菌群组成和抗病力的影响。实验选取平均体重为27g的罗非鱼幼鱼为研究对象，分别用等氮等能的五种不同糖脂比饲料: 44.2/4(D1)、39.6/6(D2)、35/8(D3)、30.4/10(D4)、25.6/12(D5)，饲喂10周，采用营养学、生化分析结合高通量测序技术开展了相关测定研究。结果显示，糖脂比饲喂前期对罗非鱼生长具有显著影响，高糖或高脂饲料均生长较差，但饲喂到10周后，所有组间生长无显著差异 (P > 0.05)。相比之下，10周糖脂比在脏体比、肠系膜脂肪指数、肝体比、全鱼粗蛋白、肝脏甘油三酯、血清低密度脂蛋白胆固醇（LDL）和尿素、抗病力、菌群组成等方面存在显著效应。低糖脂比D4在脏体比上显著高于高糖脂比D1 (P < 0.05)，而在血清尿素和抗病力上显著低于D1 (P < 0.05)，在肠系膜指数上显著高于高糖脂比D1和D2 (P < 0.05)，但在全鱼粗蛋白上显著低于D1和D2 (P < 0.05)。另外，D1不仅在肝体比上高于低糖脂比D5 (P < 0.05)，而且在LDL和糖耐受能力上均高于其它各组 (P < 0.05)。与之相比，糖脂比虽在肠道微生物物种丰度和均一度上没有显著性差异 (P < 0.05)，但在物种组成和热图显示低糖脂比D4与其它组肠道菌群组成不同。D4在聚类关系上单独一支，其门水平上衣原体门、绿弯菌门、放线菌门高于其它各组，特别是D2和D1，但厚壁菌门低于其它各组，特别是D2; 属水平上，D4组幽门螺杆菌属明显多于其它组，而乳杆菌、双歧杆菌属明显少于除D3外的其它组。综上所述，罗非鱼对不同糖脂比饲料有很强的适应和利用能力，但高糖比饲料利用上强于低糖脂比。本实验条件下，高糖组中39.6/6(D2)饲料组虽然在生长上与其它各组无显著差异，但其鱼体粗蛋白含量在各组中最高，肠道菌群组成上也优于其它各组，是罗非鱼适宜的糖脂比水平。     

鲤irisin多克隆抗体的制备及应用

为进一步研究鱼类糖代谢与鸢尾素(irisin)之间的关系，亟需制备irisin抗体并检测其应用可靠性。本实验通过构建Rosetta-irisin表达载体，经蛋白纯化、透析、超滤后免疫小鼠，获得相应多克隆抗体并检测其特异性和抗体效价。建立irisin检测方法，检测口服葡萄糖耐量(OGTT)、RNAi实验后鲤血清irisinA和irisinB的含量变化。免疫荧光检测鲤脑、肠道、心脏、肝胰脏irisin的表达及OGTT后，检测上述组织irisin含量变化。检测鲤肌细胞分化前后FNDC5 mRNA表达差异及irisin含量变化。结果显示，Rosetta-irisin表达载体在IPTG诱导4 h对鲤irisinA/B蛋白表达较BL21-irisin表达载体提高2.3/1.6倍；irisinA和irisinB抗体效价分别为9.0×10⁴和2.7×10⁵，不存在交叉反应，可分别对鲤血清irisinA和irisinB进行测定；OGTT后，irisinA和irisinB呈现出不同的合成变化；RNAi后，irisin含量显著降低；免疫荧光结果显示，irisin在脑中表达最高，肝胰脏次之，心脏、肠道中相对较少；OGTT后，脑、肠道、心脏和肝胰脏中irisinA和irisinB荧光强度显著增加。荧光定量表达分析与免疫荧光结果显示，鲤肌细胞分化后，FNDC5和irisin含量显著降低。综上，本实验制备了高亲和力和特异性的鲤irisinA和irisinB抗体，并检测其应用可靠性。该抗体的获得为系统研究irisin对鲤糖代谢的调控机制奠定基础。同时，鲤irisin检测方法可普遍用于其他鱼类irisin蛋白质水平的定量研究。     

腹腔注射葡萄糖对大黄鱼血液生化指标及糖代谢关键酶表达量的影响

为研究大黄鱼对葡萄糖的耐受能力和相关糖代谢关键酶的表达量,选取体质量约为100 g的大黄鱼禁食24 h,随机分为3个实验组,分别为对照组(0.9%的无菌生理盐水,CG组),低剂量葡萄糖组(300 mg/kg体质量,LG组)和高剂量葡萄糖组(1500 mg/kg体质量,HG组)。结果显示,大黄鱼在注射高剂量和低剂量葡萄糖后,血糖均在3 h达到最高水平,且HG组的峰值显著高于LG组,LG组在24 h恢复至正常水平,HG组在24 h仍然高于正常水平。HG组、LG组注射葡萄糖后,HK、GK基因相对表达量均显著上升,其峰值出现在注射后9 h。HG组PFK基因相对表达量在注射后6 h达到峰值。HG组PEPCK基因相对表达量在注射葡萄糖后显著下降,其中最低时间点为2 h。HG组G6PD基因相对表达量在注射后6 h显著高于其他各个时间点。研究表明,注射高、低浓度葡萄糖后,均会提高大黄鱼血糖水平,且能维持较长时间。注射葡萄糖后糖酵解途径关键酶如HK、GK、PFK及糖异生途径关键酶PEPCK基因相对表达量受血糖调节,但G6Pase、FBPase表达量并不因血糖升高而下降。导致注射葡萄糖后,大黄鱼不断产生内源性葡萄糖,这是大黄鱼表现为对高血糖不耐受的原因之一。     

Comparison of a portable blood glucose meter analyzer with a benchtop point-of-care chemistry analyzer for measurement of blood glucose concentration in client-owned ferrets (Mustela putorius furo)

BackgroundHypoglycemia is common in pet ferrets (Mustela putorius furo) because of the high prevalence of insulinoma in this species. The objectives of this study were to evaluate agreement of a portable blood glucose meter (PBGM) with a benchtop point-of-care (POC) chemistry analyzer for measurement of blood glucose concentration in ferrets, and to assess the clinical impact of using a PBGM for blood glucose measurement. The benchtop POC analyzer was used as the reference analyzer (modified hexokinase method).MethodsGlucose concentration was measured from 82 blood samples from client-owned ferrets with the benchtop POC chemistry analyzer and the PBGM. Agreement and bias between measurements were assessed using the Bland-Altman method and a Passing-Bablok regression analysis. A modified Clarke error grid analysis was modelized to evaluate the clinical effect if the PBGM was used rather than the benchtop POC chemistry analyzer.ResultsGlucose values obtained with the PBGM were not in agreement with the benchtop POC chemistry analyzer, and it underestimated blood glucose concentration in many cases. However, variation was unpredictable (mean bias, -3.97 mg/dL; range, -52.2 to 64.8 mg/dL), with wide 95% LOA (-47.3 to 38.5 mg/dL). A Passing-Bablok linear regression analysis had a slope of 1.13 (95% confidence interval: 1.00–1.36), and an intercept of -20.78 (95% confidence interval: -38.92 to -9.90), highlighting presence of a proportional and a constant bias. Important clinical error would have occurred in 1% of cases with the PBGM.ConclusionUnpredictable variation of glucose results obtained with the PBGM could have an important impact on clinical decision making. Thus, the use of a benchtop POC analyzer using hexokinase method for measurement of blood glucose concentration should be favored in ferrets for rapid onsite result obtention.